Pulverizing system



March 19, 1940. H. H. MANDLE PULVERIZING 'SYSTEM Filed Nov. 16, 1936 4 Sheets-Shag?. 1

l March 19, 1940.` H. H. 'MANDLE I PULVERIZING SYSTEM 4 Sheets-Sheet 2 Filed Nov. 16, 1956 March 19, 1940.

H. H. MANDLE PULVERIZING SYSTEM Filed Nov. 16, 1936.

l @E Sk 4 Sheets-Sheet C5 March 19, 1940. H. H. MANDLE I PULVERIZING SYSTEM Filed NOV. 16, 1936 4 Shee ts-Sheet 4 Planea i9, 1940 PATENT orales;

v Pupvniuzmc SYSTEM Henry Hayman Handle, Closter, N. J., assignor, by meme assignments, to United States Metal Powders. Ine.. Baltimore, Md.

Application November 16, 1938, Serial No. 111,021

In Great Britain September 9, 1936 s claims. (ci. xs-9a) In the combination of Solid materials, for example in the reduction of metal to powder, it is usually diilicult to obtain a high yield without excessive comminution of part of the material.

5 Moreover, for economical working it is necessary to reduce vthe bulk of the charge of raw material to powder before removing it from the "pulverizing mill. If the pulverizing` operation is continued until the bulk of the charge has been coml minuted, i. e. a high yield of powder is obtained, then it is inevitable that a material proportion of the resultant powder will be reduced to avery ilne dust and there will be a continuous range of particle sizes within relatively wide limits. Thus,VV

l the resultant powder will in no way be uniform and in some cases such as the production of socalled bronze powders the ilne dust can only be regarded as waste. On the other hand, if the pul-v verizing operation is interrupted before there: is any excessive eomminution, i. e. comminution beyond the desired lower limit, then the yield is small. If then further raw material is introduced to maintain a constant quantity of material under treatment, there is a danger during the next pulverizing operation of excessive comminuton of the material which has already been partially pulverized, whereas, if after. the comminuted material of the desired size has been withdrawn. the pulverizing operation is continued with the remaining material, the quantity of material being subjected to comminution progresslv'elyv decreases and the pulverizing mill is not utilized up to capacity. Whatever mode of operation is employed, provision must be made for the very completeseparation of the product of the desired ilneness from theicoarser material.

The present invention has for its object to provide methods and .apparatus enabling v a farreaching control of the pulverizing operation, and 40 whereby Solid material can be comminuted without the production of excessively fine particles 50 The treated material can be withdrawn from the action ofthe mill before excessive reduction o f any appreciabley proportion by following the ell. known method employed in ball mills in the production of metal powders, more particularly 55 the so-called "bronze powders, namely by passing a gas Stream through the mill at an appropriate speed. Substantially. complete separation of the product of the desired degree of iineness from the coarser material can be attained satisfactorily by mechanically sifting the material withdrawn from the mill, while for the coarser product to be further comminuted but to a lesser extent than fresh material it is necessary to use a separate mill for the further reduction of the partially reduced material unless provision is 10 made for causing the partially reduced material to be exposed to a part only of the action ofthe mill to the full action of which the fresh material is subjected.

tion of the arrangement for the simultaneous and separate introduction of coarse and partially pu1 -verized material' into the pulverizing mill.

Fig. 4 is a detail view of the feed hopper for 30 coarse material.

Figs. 5 and 6 are further details showing a preferred arrangement for introducing coarse material into the feed hopper. l

In Fig. 1 the material to be pulverized is intro- 35 duced into the ball mill or other rotary pulverizing mill I by way of the hopper 2 and the worm conveyor 3. The ball mill I is driven by the motor yIl byway of the gear train 5, 6, l, 8, while the worm conveyor 3 is Vdriven independently by the motor 40 10 by way o f the variable speed transmission 'l I. A fan or blower 9 driven by a motor I! causes a current of air to circulate through the ball mill I and a lter II, cyclone or like device for Separating solid particles from algas stream. The di- 45 rectionof circulation of the air stream is indicated by the arrow' I2. Y

The material pulverized in the ball mill I is carried by the air current to the filter I I where it is entirely separated from the air stream which latter isdirected back to the drum I through the conduit I3.

The solid material separated from the air stream in the nlterf Il drops to the lower part of the filter housing which is providedwith a sight glass I4 so that the quantity of pulverized material present within the housing can be determined by inspection. Beneath the sight glass the housing is connected by way of a rotary valve I5 to a sifter I6 which by a mechanical screening operation separates the material which has attained thedesired degree of comminution from the material which is not sufdciently comminuted.V The material which is sufficiently fine is discharged from the pulverizing system by way of a conduit I1 which passes by way of a rotary valve I8 to polishing drums I9. The material which is too coarse passes from the sifter I6 by way of conduit 20 to a rotary valve 2l whereby the material can be re-admitted in regulated quantity into the pulverizing system. The material admitted by the rotary valve 2I is introduced into the air stream by means of the'mixing tube 22 and enters the ball mill I together with the gas current through the hollow shaft 23 of the Worm conveyor 3. The rotary valves I5, I8 and 2I are of the type provided with a number of peripheral pockets so that in the rotation of the valves the material introduced into the pockets on one side is discharged on the other side without any direct connection being produced between the two sides.

As the partially pulverized material is re-introduced into the ball mill I with the gas current through the hollow shaft 23 the gas current carries it beyond the range of action of the balls nearest the hollow shaft 23. The

. greater the strength of the gas current through the shaft 23, the farther the partially pulverized material is injected into the ball mill I and the less it is subjected to the pulverizing action of the ball mill. In addition there will be atendency for the lighter components of the partially pulverized material returned to the ball mill to be carried farther into the mill than the heavier components and thus subjected to a lesser pulverizing action, as is desirable. 'Ihis effect can be augmented by making use of the known ball mill of tapering cross section furnished with balls of different weights. The maximum cross section and heaviest balls are at the inlet end, where in consequence the maximum pulverizing action is exerted.

To maintain a constant quantity of materialV same rate as it is supplied to them. The sight glass I4 provided on the filter II enables the level of the material to be observed so that by appropriate control of the valve I5 the level can be kept constant and as for given working conditions the proportion ofsufiiciently finely diivided material will be constant, the valve 2| can be geared with the valve I5 so as to rotate at the appropriate speed. A transmission mechanism between the two valves I5 and 2I is indicated at 24. Alternatively, the valve 2i could be controlled independently with the aid of a sight glass in the same wayY as thevalve I5.

The mechanical sitter I6 and the rotary valve I5 can conveniently be driven froma`lcommon shaft 25, the drive to the rotary valve I5 preferably including a variable transmission 15 so that the valve can ,be controlled without inter- `fering with or modifying the operation of the mechanical screen I6. Where the device for separating the solid material from the air stream involves moving parts, these may be driven from the same shaft 25 as indicated in Figure l. number of systems as illustrated in Figure 1 are arranged side by side, a common drive shaft 12 may be provided from which the individual shafts 25 are driven.

The polishing drums I9 shown are of the customary type consisting of stationary cylinders within which brushes are rotated by means of a motor 28 and a gear train 29, 3U, 3|, 32, 33, 34. The powder passes from the upper to the lower polishing drum by a pipe 35 and the polished powder is discharged from the lower polishing drum into the collecting receptacle 36.

It is frequently necessary to provide an inert gas atmosphere in the polishing drums and provision is therefore made for passing gas through them by means of the pipe system 31, 38. These pipes do not form part of the main circulatory system as the pressure and rate of flow of the gas in the polishing drum is small in comparison with the pressure and rate of flow in the pulverizing system. In order to obtain satisfactory polishing it is frequently desirable to introduce a lubricant into the polishing drums I9 with the powder to be polished. For this purpose a lubricant dispensing device indicated at 13 in Fig. 1 is preferably associated with the rotary valve I8, so that each time a given quantity of powder is introduced by the valve I8, a corresponding quantity of lubricant is simultaneously introduced from the dispensing device 13.

When it is necessary to supply lubricant to the pulverizing mill I, the lubricating material may be introduced with the coarse material by way of the hopper 2. In many cases, however, it is unnecessary to lubricate the coarse material and in most cases it is advantageous to introduce the lubricant into the pulverizing system together with the partially pulverized material which is re-introduced for further treatment. To enable this to be donera lubricant dosing device 14 is associated with the rotary valve 2| so that each time the valve admits a predetermined quantity of partially pulverized material a corresponding quantity of lubricant is admitted simultaneously.

The association of the dispensing devices 13, 14 with the rotary valves I8, 2| not only enables 'an accuratel dosing of the lubricant to be eected,

but in addition ensures the uniform distribution of lubricant among the material to which it is added.

' Fig. 2 shows an arrangement which in its essential components is the sameas that shown in Figure 1 and corresponding reference numerals are employed to indicate corresponding parts. Certain elements of Figure l which may be employed in conjunction with Figure 2 are not shown, more particularly the mechanism for driving the rotary valve I5, the transmission between the rotary valves I5 and 2I and the lubricant dosing devices associated with the valvw 2I- and I8. The arrangement according to Figure 2 diers primarily from that of Figure 1 in that the gas'circuit for the`pulverizing system and the gas circuit for the polishing drums are interconnected so that the constitution of the gas can be controlled from a common point. In addition a. conduit 39 is provided leading from the that if necessary the entire gas current from the blower 9 can be directed solely through the filter and not through the drum I by,A closing the valves 42 'and 43.` In the normal course the current of gas passing through the drum lI is regulated vby means of the valve 43. In addition a conduit 44 ,is provided between the pressure conduit 48 and I 48 is provided with a valve 41v and can serve two4 purposes. It may be lutilized to clear any obstruction of material in the hollow tube 23 forming the shaft of the worm 3 and in addition it may be employed for controlling the composition of the atmosphere within the pulverizing mill I. By associating the valve 41 with a mixing tube device of the same character as the mixing tube 22 a volatile liquid such as furfural, furfuryl alcohol or varnolene, can be introduced into the pulverizing apparatus to reduce the oxidizing tendency of or the proportion of oxygen in the gas atmosphere in the apparatus. The volatile liquid is preferably introduced in such proportions that 'under the conditions obtaining in the mill it-is completely volatilized. rFor certain purposes more particularly when the apparatus is employed for the production of metal powder such as bronze powders, it is necessary to reduce the oxidizing tendency of the atmosphere.

In the arrangement'shown in Figure 2 the supply of gas to the polishing drums is effected by way of the conduit 48 and after passing through the polishing drums the gas enters the main circulating stream of the pulverizing system by passing through the conduit 49- to the lower part of the filter Il. A further vconduit 50 leads from the pressure conduit 40 to the point at which the constitution of the gas for thepolishing drums is controlled and completes the conduit system for the circulation of gas through the polishing vdrums.- In this way the control of the gas atmosphere is more precise in the polishing drums than in the pulverizing system where an equally high degree of precision is in general not necessary. In addition the pressure vat which the gas is supplied to the polishing drums and the rate of ow of the gas through the polishing drums can be much lower than the corresponding valves in the main pulverizing system. In particular-it is necessary that there should be a 'slower rate of flow inorder that the fully pulverized material whichisvbeing polished shouldnot be swept out of the drums bythe gas current which is provided essentially for .the purpose of ensuring the correct constitution of the atmosphere within the polishing drums.

'Ihe preferred construction of the worm o on-- veyor 3 and of the associated hollow shaft 23 which forms the subject matter of my co-pending application of even date is shown on a larger scale in Figure 3 where the hopper 2 and the pulverizing mill I are indicated in fragmentary manner. J.- The shaft A23 is rotated by means of the gear 'wheel 84 `keyed to the shaft by the pins 35. The mechanism for imparting the `drive to the gear wheel 84 is notshown in Figure 3. The rateat rate at which the worm 3 is caused to rotate by means of the gear wheel 84. The right hand end (Figure 3) of the shaft 23 is mounted in spaced bearings 81 accommodated in the xed housing 88. Packing rings 89 are provided between the fixed housing and the shaft adjacent the hopper 2 and a similar packing ring 98 is provided at the extreme 4right hand end of the shaft 23. On either side of the gear wheel 84, felt washers 9| or the like are provided between the housing 88 and the' shaft 23 to prevent the lubricant supplied to the bearings 81 from escaping. At the outer end' of the shaft 23 the housing 88 has an "extension 92, to which'the supply conduit 93 is system when the hopper 2 is being recharged.

For this purpose a slide valve I (Figure 4) is provided at the lower end of the hopper and is adapted to be positioned across the conduit leading from-the bottom of the hopper so as to isolate the hopper 2 from the main pulverizing system. The hopperitself is constructed in the form of a housing 52 provided with a filling aperture closed by a door 53. To ensure that the door 53 is not opened before the hopper 2 has been isolated from the main pulverizing system by closing the slide valve 5I, the catch 54 'serving to hold the door 53 in the closed position is preferably linked with the valve plate 5I so that the door cannot be opened unless the valve plate 5I is in the closed position which is indicated in broken lines in Figure 4. For this purpose, in the construction shown in Figure i the catch 54 is provided with a downwardly extending rod 55 carrying the operating handle 56. The lower part of this rod 55 is constructed as a rack bar 51 `which engages with a pinion 58. Rigidly conenable the door 53 to be opened lthe plate 5i is automatically interposed to isolate the hopper from the main pulverizing system. Similarly when the catch 54 is lowered to retain the door 6. Provided in the cylindrical cage are two grooves 82 and 63 which are disposed diamet rically opposite one another and extend parallel to the axis of the cylinder. A semicylindrical t ray 84 provided atone end with a corresponding semicircular end plate 85 and at the other end with a circular end plate 6i on which a handle 81 may-be provided, is filled with the material which is be introduced into the hopper. The tray M has lateral rails Il and l0 which are adapted to engage in the grooves 62 and 63 in the cylindrical cage 6l. The filled tray can thus be inserted into the rotary cage 6I and thereafter the cage and tray rotated in common within the housing 2 so as to empty the contents of the tray 64 into the hopper. If desired provision may be made for rotating the cage and tray after the door of the hopper has been closed. In this way any desired quantity of raw material can be introduced into the hopper in a simple and convenient manner.

I claim:

1. An apparatus adapted for powdering metal comprising, in combination, a ball mill having inlet and outlet ports at opposite ends thereof,l

a screw conveyor for delivering primary raw material to be powdered to the inlet port, a closed conduit system including a separator connecting the outlet and inlet ports of said mill, the inlet end of said conduit system terminating in spaced relationship inwardly of the inner end of saidscrew conveyor of the raw material, means for causing a :dow of gas through said conduit system and mill, said conduit system including means for pneumatically returning the inadequately powdered portion to the inlet end of the mill and for pneumatically projecting the mate rial into the mill by a gas blast of suiiicient intensity to deposit the material along the mill according to its size.

2. An apparatus adapted for powdering material, more particularly metal, comprising, in

combination, a ball mill having inlet and outlet ports at opposite e'n'ds thereof, mechanical feeding means for delivering primary raw material to be powdered, to and through the inlet port, a closed conduit system including a separator connecting the outlet and inlet ports of said mill, the inlet end of said conduit system terminating in spaced relationship inwardly of the inner end of said feed means of the raw material, the separator serving to separate the inadequately powdered portion from the remainder, said conduit system including means for pneumatically returning the inadequately powdered portion to the inlet port and for pneumatically projecting the material into the mill by a gas blast of suflicient intensity to deposit the material along the mill according to its size.

3. An apparatus adapted for powdering metal comprising in combination, a ball mill having inlet and outlet ports at opposite ends thereof, mechanical feed means for delivering primary raw material to be powdered to and through the inlet port, a closed conduit system connecting the outlet and inlet ports of said mill, the inlet end of said conduit system terminating in spaced relationship inwardly of the inner end of said feed means of the raw material, means for causing a flow oi' gas through said conduit system and mill, a separator, means for discharging the powdered material from the conduit system into the separator so arranged that the gas stream is prevented from passing through the separator,` said conduit system including means for pneumatically returning the inadequately powdered portion from the separator to the inlet port of the mill and for pneumatically projecting the material into the mill by a gas blast of sufllcient intensity to deposit the material along the mill according to its size, and means for independently regulating the rate of delivery of primary raw and inadequately powdered material to the mill.

4. An apparatus adapted for powdering metal comprising, in combination, a ball mill having inlet and outlet ports at opposite ends thereof, mechanical feed means for delivering primary raw material to be powdered to and through the inlet port, a closed conduit system including a separator connecting the outlet and inlet ports of said mill, the inlet end of said conduit system terminating in spaced relationship inwardly of the inner end of said feed means of the raw material, means for causing a iiow of gas through said conduit system and mill, said conduit system including means for pneumatically returning the inadequately powdered portion to the inlet end of the mill and for pneumatically projecting the material into the mill by a gas blast of sufiicient intensity to deposit the material along the mill according to its size, and means for independently regulating the rate of delivery of primary raw and inadequately powdered material to the mill.

5. An apparatus adapted for powderlng material, more particularly metal, comprising, in combination, a ball mill having inlet and outlet ports at opposite ends thereof, mechanical feeding means for delivering primary. raw material to be powdered to and through the inlet end, a closed conduit system including a separator connecting the outlet and inlet ports of said mill, the inlet end of said conduit system terminating -in spaced relationship inwardly of the inner end of said feed means of the raw material, the separator serving to separate the inadequately powdered portion from the remainder, said conuit system including means for pneumatically returning the inadequately powdered portion to the inlet port and for pneumatically projecting the material into the mill by a gas blast of suilicient intensity to deposit the material along the mill according to its size, means for indicating at the outlet end the total rate of delivery of material from the mill, and means for independently regulating the rate of delivery of primary raw and inadequately powdered material to the mill.

HENRY HAYMAN MANDLE. 

